Datasheet

Energy calculation algorithm STPMC1
68/77 Doc ID 15728 Rev 7
In case of shunt sensor (TCS = 1), an additional stage of internal digital differentiated
produces the value:
Equation 22
v
d
= dv
u
/dt = A ω cos (ω t) k
DIF
The shunt preamplifier, AD converter and calibrator produce the value:
Equation 23
vs = i R
S
(A
I
/V
REF
) k
I
= i k
S
= C sin (ω t + ϕ)
The 2
nd
stage internal integrations produce the values:
Equation 24
v
di
= ∫ v
d
dt = A sin (ω t) k
DIF
k
INT
= A sin (ω t)
Equation 25
v
si
= ∫ v
s
dt = - (C / ω) cos (ω t + ϕ) k
INT
The frequency compensated values are:
Equation 26
V
dic
= ω / k
INT
v
di
= A ω sin (ω t) / k
INT
Equation 27
v
sic
= ω / k
INT
v
si
= - C cos (ω t + ϕ)
The 3
rd
stage internal integrations and DC cancellations produce the values:
Equation 28
v
diic
= ∫ v
dic
dt = A cos (ω t) k
DIF
k
INT
= A cos (ω t)
Equation 29
v
siic
= ∫ v
sic
dt = - (C / ω) sin (ω t + ϕ) k
INT
10.1 Active energy calculation
The active power is computed as follows.
First, the voltage stream from the 1
st
stage ( Equation 13 or Equation 22 ) is multiplied to the
16-bit current from the 2
nd
stage ( Equation 16 or Equation 25 ) and current stream from the
1
st
stage ( Equation 14 or Equation 23 ) is multiplied to 16-bit voltage from the 2
nd
stage of
filter (
Equation 15 or Equation 24 ), yielding:
Equation 30
P
1
= v
u
v
ii
= - ABk
INT
sin (ω t) sin (ω t + ϕ) = - ABk
INT
[cos ϕ - cos (2 ω t + ϕ)] / 2
Equation 31
P
2
= v
ui
v
i
= ABk
INT
cos (ω t) cos (ω t + ϕ) = ABk
INT
[cos ϕ + cos (2 ω t + ϕ)] / 2